Heretofore, in a technology field of an electronic module in which an IC (Integrated Circuits) chip and other electronic component are mounted on a circuit board, there has been developed a technology by which an electronic module is manufactured at a low cost using a technology such that a metal paste (for example, a solder paste) is in advance applied (potting) to prescribed positions on a circuit board, and then the aforesaid circuit board is subjected to a reflow process (a heating process) with an electronic component being placed at the places to mount the electronic component in the aforesaid circuit board (for example, refer to Patent Document 1). In recent years, there has been studied a technology in which above technologies are employed to electronic devices such as a cell phone equipped with an imaging device.
In the meantime, as a material of the optical element used for the imaging device, a resin material is preferably used in view of easy molding. In general, as the optical element for the imaging device, thermoplastic resin, with which an injection molding is possible, is widely used. However, there was a problem such that, in the case where a reflow process, in which the imaging device or the electronic component is mounted on a circuit board in an integrated manner, is carried out, the optical element made of resin becomes soft, and thereby the optical element can not be used.
As a technology using the reflow process, there is proposed a technology by which an electronic device having an imaging device is manufactured in such a manner that an imaging device, containing an electronic member on which a socket (a lens case) is arranged, and other electronic members are placed on a circuit board and are mounted on the circuit board by the reflow process, after which an imaging lens is inserted into the socket (for example, refer to Patent Document 2). However, in such a technology, it is necessary to carry out positioning of the imaging optical system in a state that an electronic component of the imaging device is mounted on a circuit board. Therefore, it is difficult to perform correct positioning, and at the same time, a shape of the optical system is limited or the lens is limited to a simple structure of a fixed focus type, and then, other solutions have been demanded.
Therefore, the present inventors has been studying to use, in the case of manufacturing the imaging device which will be subjected to the reflow process, a high heat-resisting material, so that the imaging lens has a reflow resistant property, as a resin material for the aforesaid imaging lens, for example curable resin such as heat curable resin and light curable resin, which, once cured, forms a net-like structure which does not exhibit fluidity even at a high temperature. In the case of using the curable resin, compared to thermoplastic resin, it exhibits a high heat-resisting property, whereby it becomes possible to suppress degradation of optical performance due to softening or breaking down by the reflow process.
In general, in the imaging lens, an anti-reflection layer comprising an inorganic material is arranged on a base material in view of reducing the loss of the amount of light. Heretofore, in the case where an anti-reflection layer is arranged on base material composed of thermoplastic resin, the anti-reflection layer has been vapor deposited on the base material at 100° C. or lower to avoid softening of the thermoplastic resin.